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The existence of a race of sentient alien robots might be not just possible, but inevitable. In fact, we might be living in a "postbiological universe" right now, in which intelligent extraterrestrials somewhere have exchanged organic brains for artificial ones.

The driving factor is a pragmatic desire to improve mental capacity. Alien beings may have already reached a point in their evolution where, having exhausted the potential of their biological brains, they have taken the next logical step and opted for robotic brains equipped with artificial intelligence.

With global warming grabbing headlines, carbon-free nuclear power is gaining popularity—and with it, concerns over what to do with the spent uranium fuel. The largest long-term burial project, Yucca Mountain, has stalled, and even though uranium’s first trip through a reactor extracts only 5 percent of its energy, power plants in the U.S. don’t reprocess fuel. This is mainly because the most common form of uranium, an ion called uranyl, is extremely difficult to extract from the spent fuel rods. But a new Pac-Man-like molecule could change that.

Along with satellites and space stations, Earth is surrounded by tens of millions of pieces of floating space debris. Like any landfill, the trash is diverse, ranging from dead satellites to castaway rocket parts to flecks of paint. On average, over the past 40 years, one piece of space junk has fallen to Earth every day.